Thomsenolite with Ralstonite and Cryolite
Ivigtut (Ivittuut), Arsuk Fjord, Sermersooq, Greenland
ex. University of Copenhagen Copenhagen Geological Museum
Small Cabinet, 9.4 x 7.4 x 5.4 cm
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This is a noteworthy and attractive specimen of thomsenolite and ralstonite originating from Ivigtut, Greenland, the type locality for both species! Thomsenolite is a hydrated sodium calcium aluminum fluoride and ralstonite is a hydrated sodium magnesium aluminum fluoride; both very rare. Several areas on the specimen are festooned with well-formed, transparent to translucent, colorless crystals of thomsenolite in clusters and in sub-parallel growths composed of prismatic, monoclinic crystals. Ralstonite occurs as tiny octahedral crystals scattered on the thomsenolite. Crystals are lightly to moderately highlighted by iron oxides. This specimen, as well as the other thomsenolite and cryolite pieces in this update, were recovered during mining here in the late 19th Century to early 20th Century. Thomsenolite is named in honor of Hans Peter Jorgen Julius Thomsen who lived from 1826-1909, and was a chemistry professor at the University of Copenhagen, Denmark, and is attributed to being the founder of the Greenland cryolite/aluminum industry. Specimens such as this are few and far between today, only trickling out of old collections. The specimen is accompanied by a University of Copenhagen Museum label.